V-type four stroke engine with counter rotating balance weights canceling out first order imbalance moments of reciprocating and of rotational motion

Abstract

This four stroke V-configuration engine has two cylinder banks which have equal numbers of cylinders, angled with respect to one another at a bank angle α different from 90°. For each bank of cylinders, the angular positions of the crank shaft crank pins therefor are evenly spaced apart around the central axis of the crank shaft, and between the banks of cylinders the angular positions of a pair of corresponding cylinders are separated by a crank angle of 90°-α. A first set of balance weights is provided so as to rotate about an axis parallel to the rotational axis of the crank shaft in the same direction and at the same speed as the crank shaft, and a second set of balance weights is provided so as to rotate about an axis parallel to the rotational axis of the crank shaft in the opposite direction and at the same speed as the crank shaft. The positions and the weights of the first and second sets of balance weights are such as to cancel out the first order imbalance moments of reciprocating and of rotational motion.

What is claimed is: 
     
       1. A four stroke V configuration engine comprising: first and second cylinder banks arranged in a V configuration and angled with respect to one another at a bank angle α;   a plurality of pairs of cylinders, each said pair of cylinders comprising a cylinder of said first cylinder bank, and a cylinder of said second cylinder bank angled with respect to said cylinder of said first cylinder bank at a bank angle α;   a crank shaft having opposed axial ends and formed with a plurality of pairs of crank pins, each said pair of crank pins comprising a first crank pin for a cylinder of said first cylinder bank, and a second crank pin for a cylinder of said second cylinder bank, said first and second crank pins of each said pair of crank pins being angled with respect to one another at a crank angle equal to 90°-α;   a pair of camshafts arranged in parallel with said crankshaft, and including a first camshaft for said first cylinder bank, and a second camshaft for said second cylinder bank;   a balance shaft arranged in parallel with said crank shaft and said camshafts;   a first set of balance weights fixed to said crank shaft adjacent the opposed axial ends of said crank shaft;   a second set of balance weights fixed to said balance shaft;   a first sprocket wheel non-rotatably mounted on said crankshaft;   a second sprocket wheel non-rotatably mounted on said balance shaft, said second sprocket wheel having a diameter equal to the diameter of said first sprocket wheel;   a third sprocket wheel non-rotatably mounted on said first camshaft, said third sprocket wheel having a diameter which is twice as large as the diameter of said first sprocket wheel;   a fourth sprocket wheel non-rotatably mounted on said second camshaft, said fourth sprocket wheel having a diameter which is twice as large as the diameter of said first sprocket wheel;   and an endless chain engaging said first, second, third and fourth sprocket wheels such that the balance shaft and the crank shaft rotate in opposite directions at the same speed and the first and second camshafts rotate in the same direction as the crank shaft at one-half the speed of the crank shaft;   wherein the weights of said first and second set of balance weights and the position of the weights of said first and second set of balance weights relative to said crank shaft and said balance shaft respectively, are selected so as to cancel out first order unbalance moments of reciprocating and rotational motions in said engine.   
     
     
       2. An engine according to claim 1, wherein as viewed in a plane which is perpendicular to the longitudinal axes of said crank shaft, said pair of camshafts and said balance shaft, said crank shaft is at the apex of a triangle having a base defined between said first and second camshafts, and said balance shaft is located inside of said triangle. 
     
     
       3. An engine according to claim 2, wherein said triangle is a substantially equilateral triangle, and said balance shaft is substantially located on a bisector of said substantially equilateral triangle which passes through said apex.